When I was in high school there was a series of 4 books going around. Each one represented a season and the books were about an American guy trained by a Ninja clan. The idea was that the American Ninja had gone rogue and the clan sent out assassins to deal with him (Can't let their secrets get out). Each book is a different story about the assassins trying to kill him and how he survived. I cannot for the life of me think of the name. If anyone remembers such a series . . It was around 1983-86
The next great book was "Jumper" by Steven Gould
Then "Letter to a Christian Nation" by Dr. Samuel Harris